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30 June 2018, Volume 34 Issue 3 Previous Issue    Next Issue

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Application of satellite water vapor imagery and potential vorticity analysis on a neutercane-related torrential rain WU Zhi-yan, LI Hong-jiang, ZHAO Hai-jun, CONG Chun-hua, YAO Li-na 2018, 34 (3):  1-8.  doi: 10.3969/j.issn.1673-503X.2018.03.001 Abstract ( 228 )   PDF (2141KB) ( 416 )   Save Using the water vapor imagery,conventional meteorological observations and ERA-Interim reanalysis data,a torrential rain event related to typhoon and the cold air in Shandong Peninsula was studied by analyzing the water vapor imagery and dynamical fields.Results reveal that as the typhoon moving northward,the cold air of the westerly trough intrudes the typhoon circulation,the vortex cloud system combines with the baroclinic leaf-shaped cloud,and it results in a frontogenesis at lower level.The water vapor imagery shows that the asymmetric structure of typhoon is characterized by a moist ascent in the north and dry intrusion in the south of the vortex system.The dark areas with high potential vorticity in the water vapor imagery indicate the active dynamic dry bands.The axis of maximum winds is near the poleward side of the leaf boundary and along the moist side.The strengthening of the upper-level jet is associated with the sharpening of the dark/light boundary.The heavy rain area lies in rear of the jet on the right and moist ascent area ahead of the dynamic dry band.During the heavy rain process,the disturbance of upper-level PV (Positive Vorticity) caused by the dynamic dry bands results in the stretching downward of cyclonic vorticity.The column of cyclonic vorticity associated with the dynamic dry band couples with the positive vorticity column of typhoon and forms a vortex system over the area of torrential rain.The combination of ascending motion ahead of the PV anomaly and ascending motion of the typhoon circulation could have been a favorable factor to the strengthening of the moist ascending motion in the troposphere.The water vapor imagery reflects the synoptic scale forcing in the upper-level and indicates the development of important dynamical processes.A joint interpretation of water vapor imagery and upper-level potential vorticity fields can potentially provide dynamical insight into the imagery interpretation,thus provide valuable information for operational monitoring of neutercane-related torrential rain. References | Related Articles | Metrics

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Applications of densely-covered automatic weather station data in a local rainstorm event and its meso-scale feature in Dalian area LI Yan, LIU Xiao-chu, SAI Han, ZHANG Cai-feng, ZHAO Hui-fang 2018, 34 (3):  9-17.  doi: 10.3969/j.issn.1673-503X.2018.03.002 Abstract ( 243 )   PDF (6566KB) ( 230 )   Save Using the conventional meteorological data,wind field of automatic weather station (AWS) data and weather radar imagery,the meso-scale feature of a missing report local rainstorm was analyzed.The applications of the AWS data were discussed as well.The results show that the outputs from the T639,European and Japanese numerical weather prediction models demonstrate obvious deviations,and they all fail to predict heavy rain and rainstorm scenarios.Few evident forecasting indices on the background circulation and physical parameter fields can be found to indicate the heavy rain and rainstorm events.While the satellite imagery shows that the meso-scale convective cloud clusters with TBB (Temperature of Black Body) less than -45℃ consist with the heavy rainfall region.The maximum rainfall intensity region corresponds to a single-cell convective storm with the maximum echo of 55 dBz reaching 4 km and the 50 dBz echo reaching up to the height of 6 km.Its intensity is uniform.The entire feature indicates it is a low-mass-center strong rainfall radar echo.Meanwhile,the formation of a meso-scale convergence line is identified from the AWS data in the same region as the heavy rainfall happens one hour ago.The maximum convergence region shows a meso-scale cyclone feature.This feature along with the weather radar and satellite imageries can be used as an indicator for the local rainstorm alert when there is little convincing general circulation,physical parameter and the NWP output information. References | Related Articles | Metrics

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Comparative analysis of the radar echo characteristics of three heavy snowfall events in Liaoning province HU Peng-yu, XU Shuang, CHEN Chuan-lei, YANG Lei, JI Yong-ming, SUN Li 2018, 34 (3):  18-27.  doi: 10.3969/j.issn.1673-503X.2018.03.003 Abstract ( 238 )   PDF (5562KB) ( 287 )   Save Three heavy snow processes occurring in Liaoning province on March 4,2007,February 12,2009,and February 21,2017 respectively,were investigated based on the ECMWF (European Center for Medium-Range Weather Forecasts) ERA-interim reanalysis data,convention observations and echo data from the Doppler radar.The similarities and differences of the large scale circulation background,air mass source,vapor source and characteristics of the radar echo parameter of these three processes were studied.The results indicate that the three events are all caused by the influences of the upper-level trough.The upper-level trough cooperated with the surface inverted trough or cold front strengthens the dynamic lift.The air masses from different water vapor sources and the convergence of cold and warm air are the key factors to strengthen the snowfall processes.The reflectivity of the snowfall process is usually below 40 dBz,and the maximum echo depth is less than 10 km.The maximum reflectivity (Zmax) and the average value of the radar reflectivity larger than 15 dBz (Zmean15) at each level within the thunderstorm correspond very well with the process of snowfall and reveal the intensity change of the systems and the drop conditions of the precipitation particles.It is important to the forecasting of rainfall. References | Related Articles | Metrics

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Decadal characteristics of persistent heavy precipitation in the middle and lower reaches of the Yangtze River and its circulation pattern LIU Lei, ZHOU Jing, LIU Jun-jie, GAO Hui 2018, 34 (3):  28-36.  doi: 10.3969/j.issn.1673-503X.2018.03.004 Abstract ( 253 )   PDF (2376KB) ( 385 )   Save Based on the daily rainfall data of the middle and lower reaches of the Yangtze River and the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data from 1965 to 2016,the decadal change of the persistent heavy precipitation (PHP) and its circulation feature were analyzed.Results show that the peak stage of the PHP during the summer season is from June 21 to July 10.The frequency of the PHP in this period shows a similar decadal change with that in whole summer.The frequency of the PHP increases first and then decreases from 2004 to 2015.The high frequency of PHP events occur during 1989-2003.The circulation characteristics are different for the low and high frequency periods.During the period of 1965-1988,the airflow is straightness in the high-latitude region and the cold air is not active.Meanwhile,the Western North Pacific High (WNPH) is weak.It results in a weak transportation of water vapor.The perceptible water is less than the normal level and the vertical velocity is weak as well.During the period of 2004-2015,the high-latitude circulation field shows a pattern that is high in the west and low in the east at 500 hPa geopotential height.The transportation of the cold air is weak,and the Bay of Bengal trough is not strong.The WNPH is strong but located southward,so the water vapor is difficult to be transported far away to the middle and lower reaches of the Yangtze River.The preciptible water is less than the normal level as well.The high frequency of PHP exists in the period of 1989-2003,but the circulation patterns are completely opposite between the yeas with high frequency PHP and years without PHP.The high of Okhotsk Sea is strong during the frequent PHP year,and the cold air is active.The WNPH is strong and shifts westward,which enhances the water vapor transporting into the middle and lower reaches of the Yangtze River from its northwest side.Its preciptible water is sufficient.The cold and warm air intersection makes the vertical motion energetic.So,the decadal change of the PHP in this region is closely related to that of the large-scale circulation. References | Related Articles | Metrics

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Characteristics of spatiotemporal distribution and influence elements of three kinds of regional heavy fog in Jiangxi province from 2000 to 2012 CHEN Xiang-xiang, XU Ai-hua, XU Bin, XIAO An 2018, 34 (3):  37-47.  doi: 10.3969/j.issn.1673-503X.2018.03.005 Abstract ( 216 )   PDF (2321KB) ( 416 )   Save Based on the conventional surface meteorological observational data and sounding data obtained from Chinese Meteorological Administration (CMA) as well as the GD05 numerical forecasting data over Jiangxi province from 2000 to 2012,the characteristics of spatiotemporal distribution,weather situation and major meteorological parameters of three kinds of regional heavy fog in Jiangxi province were comparatively analyzed.The results show that a total of 259 regional heavy fog events occur in Jiangxi province from 2000 to 2012,and the radiative fog events occur most frequently.The radiative fog events mainly occur from late autumn to early spring,and the advective-radiative fog events mainly occur in winter.The advection fog events usually occur in late winter and early spring but not in summer.Overall,the spatial distribution of regional heavy fog in Jiangxi province is characterized by a high frequency in the middle region and low frequency in the northern and southeastern regions.A radiative fog event can cover a wide area,while the advection fog events usually occur within a narrow area.Among the regional heavy fog events in Jiangxi province,the radiative fog events are the most common type.The temperature inversion intensity is the strongest for advection-radiation fog events and is the weakest for advection fog events.The temperature inversion layer mainly exists near and under 1000 hPa level,and dry air at upper levels and wet air at lower levels.Multi-inversion layers can be found in advection-radiation fog and occur under 1000 hPa level and near 925 hPa level with high moist area.The advection fog has deep moist layer and with the thermal inversion layer near 925 hPa level.As a radiation fog event occurs,the surface pressure field is uniform and the lower levels are controlled by an anticyclone circulation over Jiangxi province.During advection-radiaiton fog events,Jiangxi province is mostly controlled by the southerly flows at the back of weak high pressures,and a wide southerly current prevails at the lower levels.When an advection radiation fog occurs,the foggy area is located near the surface depression inverted trough and is controlled by the warm and moist southerly flows within 2-latitudes distance to the south of the shear line at 925 hPa. References | Related Articles | Metrics

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Fog weather forecast experiments over Shandong province based on three visibility schemes XIA Fan, LI Chang-yi 2018, 34 (3):  48-57.  doi: 10.3969/j.issn.1673-503X.2018.03.006 Abstract ( 260 )   PDF (3487KB) ( 348 )   Save Based on Weather Research and Forecast (WRF)-Rapid Update Cycle (RUC) model system,three operational visibility schemes,including Stoelinga and Warner (SW) scheme,RUC scheme and Forecast Systems Laboratory (FSL) scheme,were used to make a forecast experiment for 25 fog events from October of 2015 to March of 2016 in Shandong province.The experiment included quantitative forecast of visibility and diagnostic forecast on weather fog occurs.The forecasting result is evaluated using routine meteorological observations.The causes of bad forecast on fog weather by different schemes were analyzed and then the RUC scheme was improved.The results indicated that the mean absolute error of visibility computed by the SW scheme ranges between 9 km and 12 km,while that computed by RUC scheme and FSL scheme varies within 2-4 km.For most of the fog events over Shandong province in the forecast experiment,the hit rate is larger than the false alarm rate based on the SW scheme and the FSL scheme,which means that the two schemes have a certain capability to forecast fog events.However,the hit rate and false alarm rate of fog prediction by the RUC scheme are both zero,indicating that this scheme has no ability to forecast fog.Combining the evaluating results of visibility and fog,the FSL scheme is more suitable to produce the operational product of fog in the WRF-RUC model.The major causes of bad predictive results include that the simulated visibility is very sensitive to the error of relative humidity,the influence of air pollutant on visibility is not considered,and lack of appropriate localized revision impact on the forecast effect of visibility scheme on fog.After improving the RUC scheme,the mean absolute error of the visibility deceases and the forecasting performance of fog is improved. References | Related Articles | Metrics

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Analysis of effect of precipitation events on air pollutant concentration AN Lin-chang, ZHANG Heng-de, LI Kai-fei 2018, 34 (3):  58-70.  doi: 10.3969/j.issn.1673-503X.2018.03.007 Abstract ( 670 )   PDF (2267KB) ( 345 )   Save Based on the surface observation data obtained from China Meteorological Administration (CMA) and six pollutants concentration obtained from the Ministry of Environmental Protection (MAP) of China from 2014 to 2016,the variation of air pollutant concentrations before and after precipitation was analyzed.The results show that the occurrence frequency of the decrease in six air pollutants concentration after precipitation is about 43%-60%.The decrease in PM10 concentration is most obvious,then in order of PM2.5,O3,SO2 and NO2,and least in CO.Overall,the larger of air pollutant concentrations before precipitation,the more frequently cases with decreasing concentration after precipitation occurs,and the larger the decrease value is.However,when air pollution concentrations are low before precipitation,there are many cases with increasing concentrations after precipitation,taking a proportion about 21%-61%.Because the mean air pollutant concentrations are very high in the Beijing-Tianjin-Hebei region,the decrease in air pollution concentrations is more obvious in this region than in the Yangtze River Delta region and the Pearl River Delta region.For most of the precipitation hours,the larger the hourly precipitation is,the proportion of hours with decreasing concentrations increases,but the decrease value is smaller.The difference is that when the hourly precipitation is larger than 10 mm,the decrease in O3 and SO2 concentrations in the Beijing-Tianjin-Hebei region and in PM10,PM2.5 and SO2 concentrations over the Yangtze River Delta region is smaller than that when hourly precipitation is smaller than 10 mm.The variation of concentrations of NO2 and O3 in the Pearl River Delta region is not sensitive to the hourly precipitation.The effect of precipitation on the scavenging of O3 at a relatively large concentration is very obvious in the Beijing-Tianjin-Hebei region.In the Yangtze River Delta region and the Pearl River Delta region,when CO concentration before precipitation is small,the number of cases with increasing concentration after rainfall is more than that with decreasing concentration.In addition,the effect of rainfall on the removal of SO2 is very obvious. References | Related Articles | Metrics

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Variation characteristics of evaporation in Jilin province from 1951 to 2015 XU Shi-qi, LIANG Hong-hai, FU Shuai, HU Yi-xin 2018, 34 (3):  71-77.  doi: 10.3969/j.issn.1673-503X.2018.03.008 Abstract ( 243 )   PDF (1455KB) ( 434 )   Save In this paper,the daily E601 and small pan evaporation observations,during the non-freezing period (from May to September) from the national base meteorological stations in Jilin province from 1998 to 2001,were compared.Besides,the evaporation characteristics of the small pan were investigated.Results indicate that the monthly change of averaged evaporation from 1998 to 2001 in Jilin province is significant during the non-freezing period.The evaporation of the small pan in each site is obviously larger than that of the E601 pan,and the gap between two observations decreases in the order from May to September.The annual mean evaporation in Jilin province gradually increases from the southeast to the northwest during 1951 to 2015.The spatial distributions of evaporation in spring,summer and autumn are similar to the annual situation,while that in winter is slightly different from other seasons.In recent 65 years,the annual mean evaporation in Jilin province shows a decreasing slightly trend,but the trends are different among regions and seasons. References | Related Articles | Metrics

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Temporal and spatial distribution characteristics of surface vapor pressure and their influencing factors in Weifang WANG Xiao-li, WANG Tian-ru, YANG Meng, ZHANG Na, LU Dan, XU Tai-an 2018, 34 (3):  78-85.  doi: 10.3969/j.issn.1673-503X.2018.03.009 Abstract ( 239 )   PDF (1762KB) ( 215 )   Save Based on observational data on the monthly surface water vapor pressure and other meteorological factors from 9 meteorological stations in Weifang from 1961 to 2015,the temporal and spatial distribution characteristics of surface water vapor pressure and their influencing factors were analyzed using climate tendency rate,EOF,M-K abrupt change test and correlation coefficient statistical methods,which provides a theoretical basis for the rational development of cloud water resource.The results show that in the past 55 years,the water vapor pressures in spring,autumn and winter and annual average in Weifang show an increase trend,especially in spring,while its value in summer is in a decrease trend.Interdecadal variation of surface vapor pressure in Weifang is obvious and the lowest value appears in 1980s.In addition,annual pattern of monthly mean water vapor pressure presents an obvious single peak distribution with the maximum and minimum values in July and January,respectively.Besides,the water vapor pressure in Weifang shows an increasing trend after an abrupt change occurring in 1989.The spatial distribution of annual and seasonal water vapor pressure in Weifang all indicate increasing characteristics from the northwest to the southeast and the lowest and highest values all appear in Qingzhou and Zhucheng,respectively,which is affected by the geographical position and altitude.A spatial characteristic of reverse distribution in water vapor pressure from northwest to southeast in Weifang is reflected by the feature vector.Moreover,the surface water vapor pressure is affected by many meteorological factors and has significant positive correlation with relative humidity,temperature and precipitation,and significant negative correlation with sunshine,evaporation and wind speed. References | Related Articles | Metrics

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Research on crop yield dynamic forecast based on Integration Regression Method in Heilongjiang province ZHU Hai-xia, LI Dong-ming, WANG Ming, WANG Ping, YAN Ping, LI Xiu-fen 2018, 34 (3):  86-92.  doi: 10.3969/j.issn.1673-503X.2018.03.010 Abstract ( 172 )   PDF (523KB) ( 296 )   Save Integration Regression is a new method of yield dynamic forecast because it has a clear biological significance and good effects on prediction.Adaptability of dynamic forecast to main crops was studied with integration regression method in Heilongjiang province for improving the method of dynamic forecast and making forecast accuracy better.The results indicate that the built crop yield dynamic forecast models for corn,rice and soybean based on integration regression method during late June to late September pass the test of F significance.The smaller mean difference (MD) and relative error (RE) prove that all the models have better performances.More specifically,the spring maize and rice prediction models have excellent performances and are able to reproduce practical yields well.With model testing on the basis of field experimental data from 2011 to 2014,spring maize,rice and soybean yield prediction models achieve respectively the simulation accuracies of 96%,95% and 93%,which manifests that the adaptability of integration regression method is slightly worse for soybean and better for spring maize and rice in Heilongjiang province.In another word,based on integration regression method,dynamic forecast for corn and rice is feasible in Heilongjiang province,while its adaptability for soybean will need to be further studied. References | Related Articles | Metrics

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Analysis of suitable sowing period of winter wheat in Rizhao area under climate background CHENG Zhao-jin, CHEN Lei, XU Shu-mi 2018, 34 (3):  93-98.  doi: 10.3969/j.issn.1673-503X.2018.03.011 Abstract ( 220 )   PDF (589KB) ( 284 )   Save Climate change has changed the breeding environment of crops.More specifically,the increase of accumulative temperature in winter has changed the suitable sowing period of winter wheat (SSPWW).The spring frost and dry-hot wind have damaged the physiological function of wheat.To guide agricultural production better,it is important to determine the optimum sowing period of winter wheat in the context of climate change.Based on the daily meteorological data of 3 meteorological stations in Rizhao area from 1951 to 2016,using the methods of trend analysis and correlation test,the spring frosts duringthe SSPWW the effective accumulative temperature ≥ 0℃ is 400-750℃·d before winter,during the wheat's jointing stage and the temporal and spatial variation of high temperature dry-hot wind weather during the wheat's milk-ripe stage were investigated.The results show that the effective accumulative temperature ≥ 0℃ before winter i.e.the period during October 2 to December 20 increases with a ratio of 1.572℃·a-1 at Donggang district in recent 62 years,of 1.339℃·a-1 at Wulian County in recent 58 years and of 1.513℃·a-1 at Ju County in recent 66 years.In addition,the SSPWW in Rizhao area does not occur an abrupt change.As a result,the SSPWWs at Donggang District,Wulian County and Ju County are confirmed as the periods during October 20-25,October 17-20 and October 11-15,which are 5-10 days later than traditional sowing periods and theoretically avoid frost damage in the winter wheat's jointing stage as well as decrease high temperature dry-hot wind damage for 69%,85% and 75% in the wheat's milk-ripe stage,respectively.In short,this study plays a positive role in guiding local winter wheat production. References | Related Articles | Metrics

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Relationship between daily maximum electric power load and meteorological factors in summer in Beijing LI Chen, GUO Wen-li, WU Jin, JIN Chen-xi 2018, 34 (3):  99-105.  doi: 10.3969/j.issn.1673-503X.2018.03.012 Abstract ( 200 )   PDF (671KB) ( 347 )   Save Based on daily electrical load data in Beijing from 2006 to 2013 and meteorological observation data in Beijing plain areas including Chaoyang,Haidian,Fengtai,Shijingshan,Beijing Meteorological Observatory,and Changping,the spatial and temporal characteristics of electrical load and the relationship between summer maximum electrical load and meteorological factors were analyzed.Three methods were used to extract meteorological load.The correlation between meteorological factors and summer meteorological load was also analyzed.The results show that daily electrical loads increased linearly from 2006 to 2013.The patterns of annual and hourly variations both present obvious "bimodal pattern".Usually,the maximum electrical load appears in summer,but in some districts,it appears in winter.Electrical loads in Chaoyang and Haidian districts are significantly higher than those in other areas.The maximum electrical load in summer in Beijing significantly correlates with temperature humidity index and daily mean temperature.The correlation coefficients between meteorological factors and meteorological load are higher than those between meteorological factors and original load.The extraction method based on eliminating summer mean maximum variation trend is better than other methods.When the accumulated meteorological factors amount to 2 days,the summer meteorological load is the most sensitive to the meteorological factors. References | Related Articles | Metrics

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Effects of meteorological conditions on highway traffic safety in Liaoning province LIN Yi, LI Qian, ZHANG Kai, LI Lan, QI Xin, LIN Zhong-guan, LIN Song, ZHANG Yun-fu 2018, 34 (3):  106-111.  doi: 10.3969/j.issn.1673-503X.2018.03.013 Abstract ( 213 )   PDF (581KB) ( 412 )   Save Based on highway traffic accident data from 2010 to 2015 in Liaoning province,including geographic position,level of accident and environmental condition,highway traffic accident index was quantified based on the level and the number of accidents using order relation analysis method.By matching the accident location with the nearest meteorological observation station,correlation relationship between meteorological factors and traffic accident number was analyzed.A stepwise regression analysis was proposed to estimate highway traffic accident index based on meteorological factors.The results show that the years with high frequency of highway traffic accidents are characterized by more precipitation and less sunshine hours.The number of accidents caused by weather and average highway traffic accident index are the largest in winter.The correlation relationship between highway traffic accident index and relative humidity (or precipitation) is better than that with other meteorological factors.The stepwise regression method is used for simulating highway accident index based on meteorological factors.It suggests that the prediction accurate rates of major accidents in winter and autumn are higher than those in other seasons,and they are 62.5% and 51.3%,respectively. References | Related Articles | Metrics